Electric wave circuit



R. K. HONAMAN ELECTRIC WAVE CIRCUIT Filed May 28, 1941 April 14, 1942.

ao ourpur lNVENTOR R. K HONAMAN ATTOR EV Patented Apr. 14, 1942 zgzi'sisre v ELECTRIC WAVE cmcUi'r, Richard K. Honainan, Glenfiidge,N." J., assign or to Bell Telephone Laboratories, 'liicorpo rated, New York, N. Y.,

York

"a corpcr'ation of New Application May 28, 1941,,saa1m 395,551 5 01mins.- (c1. 25'0 3e)' This application relates to electric :vvave circuits and, moreparticularIy to a multifrequency i n r t n .emit I s i Many communication systems involve the use f a p u y orh u r quen r ecfiii? a rier waves I-n power linecarrier frequency telephone t s f ex mp i h sbe e P posed to use'one carrier wave for signaling purposes and asecondor more carrier .wavesfor talking purposes between the subscriber stations 19 coupled tothe power line. In power line carrier frequency telephone systems, for example; 'it has been proposedfalso to use voice operated devices which iunctiqn in such a manner that a sube scribers'car'rier irequencyis producedcnly when he is talking and his receiver is sensitiveto 'sig na spn r h h s l te I h re uen y output oi a m-ultifrequency oscillations-source is controlledby voice frequency signals then one of its frequencies could be used for the carrier vvh ilethe other could be employed 'as the beat scillator frequency in a heterodyne receiver. Thus,, when voice signals are present; the carrier frequency is produced, which enables trans rnisfsion While at the same time the beat frefluency tor, the heterodyne receive'r is'; notproduced -so that the receiver is disabled. Similarly', when voice signals are absent, the heterodyne beat frequency i s -present and the receiver is enabled, while the carrier frequency is absent,

so tl'l at thetransmitter is disabled. p the standpoint of economy and simplicity of circuit, it would be desirable if the high "frequency vvaves required in the particular system could be obtained froma single source and pr e ferablywith the use of a single electron discharge device. When a single electron discharge deviceis used, a plurality of tuned circuits each resonant at a different frequency are associated 'vrith and eans are provided for selectingthe particular tuned circuit enabling the generation o f sustained oscillations ofthe desired frequency. It vvould bra-advantageous to have this Selection of circuits take place automatically and, when only two different 'frequenciesfare involved, to have the shifting from oneffrequency to the other be correlated with biasing potentials applied to a plu ralityof grids or control electrodes smeared the discharge device. a v

, An object of the invention is to improve and R simplify"mnltiple frequency oscillations-generating circuits I InI accordance with the invention a pair of timed circuits are associated with two grids in a inultigrid electron discharge device in whicheach I of t egrids is arranged to functionas a control electrode for a separate electron-stream between the cathodeand the anode of the discharge week vice. Each of the tuned circuits is located in a cathode-grid circuitand is vsuitably coupled to r the; cathode-anode circuit so that thereisregenerative feedback with vrespect to each or the tuned circuits. The potentials on the gridsfare initially; such that one grid is biased beyond out: oif whereby sustained oscillations arehprevented iii-the tuned circuit associated with it. The oscillationsgenerated in the other tuned circuit may be detected at suitable output terminals for the electric circuit. Associated with the cathodegrid. circuits is means responsivefto voice .fre.-'

quency signals or currents vto reverse thejnitial biasconditions of the grids, whereby. the formerly enabled and disabled oscillationsgenerating; 1r;-

cuits are respectively disabled and. enabled sol'o'hg voice irequency signals are incoming tosuch v A more complete understanding of the invention. will be obtai'ned from the detailed description that follows taken in conjunction with the appended drawing, thesingle 7 figure of which discloses a circuit arrangement embodyingthe invention. j

The circuit comprises an amplifier stage 'Aga rectifier or j'detecting' stagecR and an oscillator 'sta'geO. The amplifier stage comprisesva threejelectrodevacuum tube or electron dischargede vice H) havingan indirectly heated cathode l-' I connected to ground, a control electrode or grid l2 connected tothe-input potentiometerhl3, and

anoutput electrode or anode l4 connected to the primary winding of transformer l5. -The input;

potentiometer, shown in'se'ries with a capacitance I6, is! connected to a suitable source of electrical energyffor example, of voicefrequency currents or signals. [Anode potential and space current for the tube vIll are supplied from battery B or from an equivalent rectifier.

The rectifier stage comprises adiodeior twoelectrodeyacuum tube 20, the anode 2| of which is. connected to one terminal of the secondary winding of transformer IS, the other terminal of the secondary windingbeing connected to ground through a resistor, 22. The indirectly [heated cathode 23 is also connectedto ground through a second re'sistor, 24,,the junction of the cathode andof resistor 24 being connected with the high potential or/positive terminal ofa current source or batteryi25. By-pass condensers 25, 21, 28 are connectedfin shunt with each of the resistors 22, 24 and with battery 25;

- The oscillator stage comprises a multigrid vacuum tube or electron discharge device 40. comprising an indirectly heated cathode 4l connected to ground, an anode 42 connected through coil 43' to the positive terminal of battery B, and

a pair of grids or controlelectrodes 44, 45. One grid 44 is connected througha grid-biasing resistor and by-pass condenser network 46 and a denser network 49 and a secondtunedcircuit N2 comprising a coil 50 and condenserll', to the;

negative terminal of battery 25. The tunedcircuits N l and N2 are proportioned to respond to or be resonant at two different frequencies Fl, F2 respectively. The

be a portion of the voice frequency currents generated by the subscriber at the station in talking. The circuit, however, is not to be considered as limited in utility to such a system, but is adapted to be incorporated in any system in which a source of a plurality of electric waves of different frequencies is required.

,What is claimed is: H

1. An electric circuit comprising an electron discharge device having a cathode, an anode and a pair of control electrodes, a feedback connecti on from said anode to each of said electrodes,

an oscillatory circuit connected between each ,electrode and said cathode, means for biasing cathode-anode circuit coil 43 is coupled to the coils 41, 50, thelatter being coupled to a fourth or oscillator stage output coil 52 whose ends are connected to ajpair of, output terminals 60. -*Each of the grids 44, 45 of tube is arranged toc'ontrol a separate eleetronstream betweenthe cathode; 4| and anode 4 2, and is initially biased byvirtue of grid currentjfiow in the resistors of newo'rks 46, 49. In-the absenee of any additional bias on either grid, such initial bias isnot "suificient' toprevent} sustained oscillations each of the tuned circuits N l, N2 as aresult 0f the feedback through coil' 43 from" the cathodeanode circuit to the cathode-grid circuits. Ba ttery 25 j however, in the absence of any output from the rectifier 20, provides such'an additional negative bias onth e grid that the. latter is over-biased andpsustained oscillations in'--the tunedpircuit N2 are prevented. The oscillator outputtappearing at' the'terminals will be, therefore'a wave of frequency Fl only.

When voice frequency currents or signals are J impressed on the cathode-grid circuit of the am- 'plifler ;tu be,- l0. through" the potentiometer l 3, the am'plified signals are applied to the electrodes of therectifier tube20 th'rough thejtransformer l5ir The 1 rectifier'outputfl is developed across the resistors 22, 24. The potential 'drop across resistor24 opposes that of the battery25, theibias on the grid 45 becoming that'provided by the network 49 'wherebysustained oscillations 'oflfre'quency F2 are generated'in tuned circuit 'NZand appear across the terminals 601' tSimulfltaneously, the potential developed across resistor .22 ;over -biases the. grid 44, wherebygeneration 'of .,sustained oscillations in thetuned circuit Nl is prevented. The oscillator output frequency is thus shifted from frequency Fl to frequency F2.} When the signalinput'jto the amplifier terminates the oscillator ,circuitilrestores to, its

Iqriginal conditiom-ina'smuch as the potential of, the battery 25 is no longer balanced or opposed by 'a potential across resistor, and, no'biasing potential is developed across resistor, 22

said electrodes to potentials disabling one and enabling the other of said oscillatory circuits, and means for simultaneously changing the bias on said electrodes enabling and disabling respectively the formerly disabled and enabled oscillatory circuits.

f2, An electric circuit comprising an elect'ron discharge devicehavinga cathode, an anode and a pair of control electrodes, affeedback'connection fromsaid anode to each of saidelectrodes, an foscillatory circuit connected betwee'n each electrode ,and said cathode, means forbiasing said electrodes to potentials disabling one'and enabling the other of said oscillatory 'circuits, and audio frequency operated means forsimul- 'taneously changing the bias on said electrodes enabling and disabling respectively'the formerly disabled and enabled oscillatory circuits.

.3. An electric circuitfcomprising an electron discharge device havinga cathode, ananode, anda, pair of control electrodes; a'feedbackcoil and a source of. anode potential and space currentin series between said cathode andan'ode; a grid-cathode circuit comprising one of said 4 grids, a grid leak and-condenser network, an

. If the circuit described were includedlin each ,na'ls' 60 lwould beconnectedto the power line ithrough suitable intermediatej circuits at the station. The intermediate circuit would include an appropriate signalingkey so that the normal,

output. frequency Fl would, be supplied gtothe fof fthe subscriber stations in a power line carrier ffrequencyitelephone system, the'output termi-' oscillatory circuit resonant to a preassigned frequency a source of biasing potential for said one grid for biasing it to beyond cut-oil, aresi'stor and said. cathode; 'a second grid-cathode circuit comprising the; other of said, grids, a-se'cond -grid leak and condenser network, a second oscillatory circuit resonant to a preassigned second frequencyfa second resistor andsaid cathode, said 'resistors' having a terminalin common at cathode potential and said feedback coilbeing coupled to said oscillatory circuits an outputcoil coupled tosaid oscillatory circuits; and means forde veloping a potential across] said resistors, whereby the efiect on said, onegrid of said source of biasing potential is balanced out and the second grid is biased tobeyond cut-off.

45An electric circuit comprising angelect'ron {discharge device havinga cathode, an anodeand a; plurality of grids eacharranged to control a separate electron stream between said cathode and anode, a pair of resistors connected in series. a connection from one outer end of said seriesresistors to one. ofsaid grids, said connection including. a'sourceof potential for biasing said one grid to block one of said electron streams, a connection from the other outer end of said seriesresistors to a second one of said grids, said sec- 'ond grid normally being .biased'to a potential to maintain a secondelectron stream, and means ,connected to the outerends of. said series-resistors causing current'fiow through ,said resistors whereby, so long as said current flow continues, the potential, difference developed between the ends of one resistorj counteracts the electron streamblocking effect of the source 'of bia'sing put from frequency Fl "to frequency F2 could "potential connected to said onegrid and the potential difference developed between the ends of the other resistor biases said second grid and the latter blocks said second electron stream.

5. An electric wave circuit comprising an electron discharge device having a cathode, an anode and a plurality of grids, each grid being arranged, to control a separate electron stream between said cathode and anode, a pair of resistors connected in series and having a common terminal maintained at cathode potential, a com nection from one outer end of said series-resistors to one of said grids, said connection including a network tuned to a preassigned frequency and a source of potential for biasing said one grid to block one of said electron streams, a connection from the other outer end of said series-resistors to a second grid, said second connection including a second network tuned to a preassigned second frequency and said second grid normally being biased to maintain a second electron stream, a

feedback coupling from the cathode-anode circuit to each cathode-grid circuit whereby sustained oscillations of said second frequency are generated in said second network, and means connected to the outer ends of said series-resistors for establishing current flow therethrough whereby, so long as said current flow continues, the potential difference developed between the ends of one resistor counteracts the electron stream blocking effect of said source of biasing potential and enables generation of sustained oscillations of preassigned frequency in the firstmentioned tuned network, and the potential difference developed between the ends of the other resistor biases said second grid such that the latter blocks said second electron stream and said second tuned network is disabled as to generation of sustained oscillations at said second frequency.

RICHARD K. HONAMAN. 

